1) Field of the Invention
The present invention relates to a magneto-resistance effect type head that records (writes) and reproduces (reads) information in and from a magnetic disk of a magnetic disk drive or a hard disk drive (HDD) included in a large-scale general-purpose computer (main frame).
2) Description of the Related Art
The currently available magnetic HDDs of computers have larger capacities. In association with an increase in the capacity of the HDDs, there has been the growing need for magnetic heads capable of supporting high density with high performance and high reliability. The magneto resistive head (MR head) disclosed in Japanese Patent Application Laid Open No. Hei 10-241333 supports high density.
MR heads are magneto-resistance effect type heads that operate based on the magneto-resistance effect. The MR heads have magneto-resistance effect type elements for use as a head for reproduction. Electric resistance of the magneto-resistance effect type element vanes according to intensity of the magnetic field applied. The MR heads have better sensitivity to magnetic field as compared to the thin film heads. Therefore, the MR heads output a read signal with high output even if the recording density is high, without depending on speed of a recording medium (magnetic disk).
The MR head is assembled by a slider for fixing the MR head and a flat spring (suspension) to form a head gimbal assembly (HGA), and the HGA is mounted on a magnetic disk drive. The MR head serves to only read the data, and therefore, the thin film head is used to write the data.
Conventionally, when the MR head is to be manufactured, an annealing treatment (heat treatment) is first executed to the MR head, and after the MR head is assembled with the suspension to form a HGA (after HGA is finished), a magnetic field applying process (100 to 30000 e) is executed to the HGA. The magnetic field applying process is executed because directions of easy magnetization are made to an identical direction to correct deviation in a direction of magnetic intensity. In other words, if a write signal is varied (variation in level of the write signal) when data is to be written to a magnetic disk (recording medium), deficiency such as inaccurate data read (reproduction) may occur. Therefore, it is required to perform write using a constant output signal without variations in its output. In the conventional technology, by performing the annealing treatment (heat treatment) on the MR head and the magnetic field applying process on the HGA, it is possible to stabilize outputs, i.e., variations in intensity of a signal used to read.
However, the method of manufacturing a magneto-resistance effect type head in the conventional technology has a problem as follows. That is, in this method, outputs are stabilized by executing the magnetic field applying process after the annealing treatment (heat treatment) is performed on the MR head and the MR head is finished as HGA during a manufacturing process of the MR head.
The current stat of this technology is such that even if such an annealing treatment (heat treatment) and a magnetic field applying process are executed, there are still many MR heads that have output variations. As a measure to resolve the output variations, there is also a method of subjecting the MR head to heat treatment while executing the magnetic field applying process after HGA is finished. In the case of the processing method, heat treatment is executed to the whole except for an element portion forming the MR head, which causes occurrence of pealing of the MR head due to deformation of the suspension forming the HGA and degradation (heating) of an adhesive used to fix the MR head. As a result, it is impossible to set a heat treatment temperature for the HGA to high, and therefore, insufficient heat treatment is executed. Thus, it is impossible to stabilize output variations.